This invention is based on and claims priority to Japanese Patent Application No. 2000-210350, filed Jul. 11, 2000, and Japanese Patent Application No. 2000-210351, filed Jul. 11, 2000, the entire contents of which are hereby expressly incorporated by reference.
1. Field of the Invention
This invention relates to an engine for a watercraft, and particularly to an improved induction and charge forming system of an engine for a watercraft.
2. Description of the Related Art
Personal watercraft have become popular in recent years. This type of watercraft is quite sporting in nature and carries a rider and possibly one, two, or three passengers. A relatively small hull of the personal watercraft commonly defines a rider""s area above an engine compartment. An internal combustion engine frequently powers a jet propulsion unit that propels the watercraft. The engine lies within the engine compartment in front of a tunnel (e.g., a recess) formed on the underside of the watercraft hull. The jet propulsion is located within the tunnel and is driven by a driveshaft. The driveshaft usually extends between the engine and the jet propulsion device through a wall of the hull tunnel.
Personal watercraft are commonly powered by two-cycle engines, which have the advantage of being fairly powerful and relatively light and compact. However, two-cycle engines typically produce a relatively large quantities of carbon monoxide and various hydrocarbons. To reduce these emissions, fuel injection systems have replaced carburetors in some watercraft as the engine charge former. In such fuel injections systems, fuel can be injected into an induction system of the engine upstream of the combustion chamber. The principal advantage of fuel injection systems is that the amount of fuel injected into the combustion chamber can be precisely controlled. By precisely controlling the amount of fuel injected, the fuel/air ratio within the combustion chamber can be optimized to reduce emissions.
As with two-cycle engines with carburetors, the amount of air supplied to the combustion chamber typically is controlled by a throttle valve that is disposed in an air intake passage of the induction system. The throttle valve, in turn, is coupled to a throttle lever. A rider of the personal watercraft can control the position of the throttle valve through the throttle valve. In general, as the throttle valve opens, the output of the engine tends to increase.
Fuel injection engines typically include an engine control system for determining and controlling the fuel/air ratio. The engine control system typically calculates the amount of air entering the combustion chamber and then determines the amount of fuel to inject through the fuel injectors to achieve the desired fuel/air ratio. The amount of air entering the combustion chamber can be determined from the position a throttle valve sensor, which senses the position of the throttle valve. The amount of fuel injected through the fuel injectors typically is determined by measuring the fuel pressure at the fuel injectors and controlling the duration that the fuel injectors are open.
There are, however, several problems associated determining the position of the throttle valve and the amount of fuel injected through the fuel injectors. For example, in a multi-cylinder engine, the induction system typically includes several throttle valves (e.g., one throttle valve per cylinder). The multiple throttle valves in some engines are attached to a single throttle valve shaft. A pulley, which is attached to one end of the shaft, is used to rotate the shaft. As the throttle shaft rotates, the torque applied to the pulley can cause the throttle valve shaft to twist and/or bend. This can result in a difference between the position of the throttle valve closest the pulley and the throttle valve furthest from the pulley. These differences can result in an inaccurate determination of the amount of air entering each cylinder.
With respect to the fuel injectors, this component can become damaged during operation of the watercraft. For example, the fuel injectors can be damaged by heat that is generated by some engine components, such as, for example, the exhaust system. Moreover, because of its sporting nature, personal watercraft are often tilted on its side or are flipped over by advanced riders during use. As such, water can accumulate within the engine compartment. This water may splash upon and also damage the fuel injectors. If damaged, an inaccurate amount of fuel may be injected into the combustion chambers.
Therefore, a needs exists for a personal watercraft with an improved induction and charge forming system that results in more accurate measurement of the throttle position and/or the amount of fuel being injected into the combustion chambers.
Accordingly, one aspect of the present invention is a small watercraft comprising a hull defining an engine compartment. An internal combustion engine is disposed within the engine compartment. The engine has an engine body containing at least one combustion chamber and an output shaft that drives a propulsion device of the watercraft. An induction system is arranged within the hull to supply air to the combustion chamber. The induction system includes at least one intake conduit, at least one throttle body that communicates with the intake conduit, and at least one intake box. The intake conduit has an outlet end connected to the engine body and extends generally away from the engine body. The throttle body is connected to an inlet of the intake conduit and also generally extends away from the engine body. The intake conduit and the throttle body define an intake passage. The intake box is connected to an inlet end of the throttle body. The engine further includes at least one fuel injector that is connected to a fuel delivery conduit and is arranged to inject fuel into the intake passage. The intake box defines a recess in which at least a portion of the fuel delivery conduit or the fuel injector is at least partially disposed.
Another aspect of the present invention is a small watercraft comprising a hull defining an engine compartment. An internal combustion engine is disposed within the engine compartment. The engine has an engine body containing at least one combustion chamber and an output shaft that drives a propulsion device of the watercraft. An induction system is arranged within the hull to supply air to the combustion chamber. The induction system includes at least one intake conduit, at least one throttle body that communicates with the intake conduit, and at least one intake box. The intake conduit has an outlet end connected to the engine body and extends generally away from the engine body. The throttle body is connected to an inlet of the intake conduit and also generally extends away from the engine body. The intake conduit and the throttle body define an intake passage. The intake box is connected to an inlet end of the throttle body. The engine further includes at least one fuel injector that is connected to a fuel delivery conduit and is arranged to inject fuel into the intake passage. The intake box defines a shield positioned generally above or generally below at least a portion of the fuel delivery conduit or the fuel injector.
Yet another aspect of the present invention is a small watercraft comprising a hull defining an engine compartment. An internal combustion engine is disposed within the engine compartment and has an engine body containing at least one combustion chamber. The engine also includes an output shaft that drives a propulsion device of the watercraft. An induction system is arranged within the hull to supply air to the combustion chamber. The induction system including at least one intake conduit, at least a first throttle body and a second throttle body that communicate with the intake conduit, and at least one intake box. The intake conduit has an outlet end connected to the engine body. The throttle body is connected to an inlet of the intake conduit. The intake conduit and the throttle body define an intake passage. The intake box is connected to an inlet end of the throttle body. At least one fuel injector is connected to a fuel delivery conduit and is arranged to inject fuel into the intake passage. The first throttle body includes a first throttle valve positioned on a first throttle shaft. The second throttle body includes a second throttle valve positioned on a second throttle shaft. A pulley is mounted on either the first or second throttle shaft and disposed between the first and second throttle bodies. The pulley being coupled to a throttle operator.
Further aspects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments.